Phytic acid is the main storage of P in plants, and most P in plant feed ingredients is bound in the phytate complex. Because pigs do not secrete phytase, an enzyme to hydrolyze inositol bonds in phytate, the utilization of P by pigs is very low. Addition of supplemental phytase to diets thus results in release of P and increases P utilization by pigs. However, all enzymes have a special recognition mechanism called specificity that works only with molecules that fit to active sites of the enzyme. Therefore, it is important to know how much of P is phytate-bound and how much of the P in a given diet is not phytate-bound.

In the U.S. and most other developed countries, animal-based proteins provide a significant portion of the human diet. However, predictions for animal protein consumption indicates that consumption in Europe and North America will begin to decline by 2035 because plant-based proteins have become accepted as having an appearance, texture, and taste that is close to that of animal products. Examples of plant based proteins that are already on the market are plant-based burgers such as the Impossible Burger and the Beyond Burger, which are produced primarily from soy and pea protein, respectively. The digestible indispensable amino acid score (DIAAS) is recommended by FAO as the best method to determine protein quality in human foods. This method allows for calculation of the protein value of both individual ingredients and combined meals consisting of several proteins. Previous research in our laboratory demonstrated that values for DIAAS obtained in milk and breakfast cereals are additive in mixed meals, and the principle of additivity is believed to be applicable to all types of combined meals, but additional research to demonstrate this is needed. Therefore, the objectives of this experiment were to determine DIAAS values for animal and plant-based burgers and test the hypothesis that DIAAS calculated for a burger and a burger bun are additive in a combined meal.

Dried whey is often used as a source of lactose in diets for weanling pigs. Whey is a co-product from dairy processing plants that is generated after fat and protein in milk has been used to produce cheese. Whey powder is therefore, low in protein because the majority of the milk protein ends up in the cheese during processing. However, some of the cheese that is produced may not be suitable for human consumption, but can instead be used as a feed ingredient for pigs after being blended with other ingredients to improve flowability and handling.  One of the cheese co-products that is currently being marketed contains 40 to 50% crude protein and has a high digestibility of amino acids. There is, however, limited information about the energy value of cheese co-products fed to pigs although it is expected that because of the high concentration of fat in cheese, the energy value will also be high. Therefore, it was the objective of this experiment to test the hypothesis that digestibility of energy and concentrations of digestible energy (DE) and metabolizable energy (ME) in a cheese co-product is greater than that in fish meal and enzyme treated soybean meal when fed to weanling pigs.

Conventional breeding of corn has generated a new variety (i.e., high-oil corn; Byron Seeds LLC, Rockville, IN), which is believed to contain more oil and phosphorus than conventional corn. Because of the increased oil, it is possible that high-oil corn contains more digestible energy (DE) and metabolizable energy (ME) than conventional hybrids, but this hypothesis has not been experimentally verified. Inclusion of microbial phytase in diets for pigs usually improves digestibility of P because phytase hydrolyzes the ester bond that binds P to the phytate molecule in corn. However, there are at this point no data for effects of adding phytase to diets containing high-oil corn and no data to demonstrate the nutritional value of high-oil corn. Therefore, an experiment was conducted to test the hypothesis that the standardized total tract digestibility (STTD) of P, as well as concentrations of DE and ME in high-oil corn are greater than in conventional corn. The second hypothesis was that inclusion of microbial phytase to diets improves the STTD of P in corn sources.

To obtain accurate values for metabolizable energy (ME) in diets and ingredients, an accurate estimation of gross energy (GE) in urine is required. Urine samples are often prepared following the freeze-dried cotton-plastic bag method and GE is determined by the ignition of the sample in a bomb calorimeter. However, the concentration of GE in urine can also be determined by dripping urine on a cellulose pellet, which can then be ignited in a bomb calorimeter. Alternatively, energy in urine can be calculated from the concentration of N in urine assuming that all energy in urine originates from N. The latter 2 methods may be less expensive and less time consuming than using the freeze-dried cotton-plastic bag method. Likewise, oven drying instead of freeze drying of samples may reduce time and cost of the drying procedure. However, to our knowledge, no data comparing values for GE in urine and ME in diets among different sample preparation and drying methods are available. Therefore, the objective of this study was to test the hypothesis that there are no differences in GE of urine or ME values of diets among sample preparation methods (freeze-dried cotton-plastic bag, undried cellulose pellet, or N value method). The second hypothesis was that drying method (freeze drying or oven drying) of cotton-plastic bag urine samples from pigs do not influence analyzed the GE in urine or calculated ME in diets.

Whey, which is a co-product from dairy processing plants that extract fat and protein from milk to make cheese has been used in diets fed to weanling pigs as a source of lactose. Whey powder does not contain much protein because the majority of the milk protein ends up in the cheese during processing. However, cheese co-products, which contain 40 to 50% crude protein may be used in the feeding of pigs but there is limited information about the nutritional value of cheese co-products fed to pigs. Therefore, it was the objective of this experiment to measure the apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of amino acids (AA) by weanling pigs in a cheese co-product and compare values to those obtained in fish meal and in a source of enzyme treated soybean meal (HP 300).

Microbial phytase is usually included in diets for pigs to increase P absorption and utilization by hydrolyzing phytate within the gastrointestinal tract of pigs. High doses of phytase (i.e., > 1,000 FTU/kg) is also hypothesized to increase release of nutrients other than P due to increased degradation of phytate. A next generation biosynthetic bacterial 6-phytase (PhyG; DuPont Animal Nutrition) may increase digestibility of nutrients in diets for pigs; however, there are no data to demonstrate the efficacy of this phytase. Therefore, an experiment was conducted to test the hypothesis that the negative impact of phytate is reduced at higher phytase doses. It was also the objective of this research to test the hypothesis that inclusion of increasing levels of phytase increases bone ash and apparent total tract digestibility (ATTD) of minerals in diets containing varying phytate concentrations.

In most AA digestibility experiments collection bags are changed at least every 30 min and the collected ileal digesta are stored at –20 °C to prevent microbial degradation of proteins. Other attempts to reduce microbial activity in digesta include adding acids to collection bags to reduce the pH in ileal digesta. Acids may also be added to collection pitchers. However, in some experiments, no attempt to reduce pH is made because it is assumed that the rapid reduction in temperature after collection is sufficient to prevent microbial degradation of proteins.

To our knowledge, there is, however, no information about the necessity of adding acids to collected digesta and it is not known if values for apparent ileal digestibility (AID), basal endogenous losses of AA, or standardized ileal digestibility (SID) of AA are influenced by addition of acids to digesta. Therefore, the objective of this experiment was to test the null-hypothesis that values for AID, basal endogenous losses, and SID of AA are not influenced by addition of acids to ileal digesta collection bags or to collection pitchers.